Slifer Red (Osiris Red in the Japanese version) is the lowest-ranked of the three dorms at Duel Academy. The reason for why Slifer Red is ranked as the lowest of the dorms traces back to Seto Kaiba’s defeat by Yugi Muto’s Slifer the Sky Dragon during the Battle City arc.
The students, save for a select few are categorized as being the weakest duelists among the dorms, having very weak decks and poor strategies which cause them to lose most of the time. In some cases students from this dorm have never won a duel at all and drop out.
The head of the Slifer Red Dorm, in the anime, was previously Professor Lyman Banner. After Banner (as Amnael, the 7th Shadow Rider) lost a duel to Jaden Yuki his body was destroyed but his cat, Pharaoh, caught Banner's spirit in his mouth to stop him from leaving. Currently, the Slifer Dorm is run by a cat. In the manga the head of the Slifer Red Dorm is Midori Hibiki.
In the beginning of the anime Dr. Crowler expressed a great dislike for the students in this dorm, going as far as to set up stakeouts and rigging duels to find any opportunity to expel Slifer students. The students in Obelisk Blue shared his dislike and usually exploited the Slifers' low ranks by calling them names such as "Slifer Slacker", "Slifer Slime", or "Slifer Scum" (in the Japanese version, they were commonly called "dropout boys"). However, as time continued, students from all dorms began flocking to Slifer Red. Examples include Alexis Rhodes, Tyranno Hassleberry, Syrus Truesdale, Bastion Misawa, Blair Flannigan and Chazz Princeton.
However, by the end of the series, the only student officially enrolled in Slifer Red appears to be Jaden Yuki.